What's the definition of "spy"?

My Macquarie Dictionary 3rd Edn says:

1. one who keeps secret watch on the action of others

2. one employed by a government to obtain secret or intelligence, especially with reference to military or naval affairs of other governments


So the reason Mark Arbib is not being described as a spy by The Age is because:

1. we don't know whether he was in the employ of the US Government

2. we don't know how secret his observations were

3. he wasn't obtaining and passing on military or naval information; simply the internal workings of Labor party politics

4. he would sue The Age for defamation.

And is a spy someone who works for an enemy or opposite entity? That could also be a reason he can't be called a spy.

So informant then?

My Oxford Dictionary and Thesaurus defines informant as:

See informer.

1. a person who informs against another
2. a person who informs or advises

1. informant, tell-tale, taleteller, stool-pigeon, US tattle-tale, colloq. supergrass, weasel, hist. beagle, sl. snitch, finger, squealer, nose, shopper, Austral. sl. fizgig, shelf, Brit. sl. grass, nark, Brit. school sl. sneak, esp. US sl. ratfink, US sl, fink, stoolie, US & Austral. sl. dog; traitor, betrayer, fifth-columnist, spy, rat, colloq. mole.
2. informant, source, reporter, correspondent, communicator, consultant, adviser, counsel, counsellor, guide, mentor.

Under the entry for "inform" -
2. turn informer, name names, colloq. scream, sl. sing, squeak, squeal, Brit. school sl. sneak (inform against or on), accuse, incriminate, inculpate, implicate, identify, betray, denounce, colloq. tell on, rat on, blow the whistle on, split on.

I'd settle for rat. It's pretty low and seems different to a sharing of resources which one might expect allied governments to engage in. I reckon it stinks and it stinks even more that he was one of the people who 'handled' the Rudd toppling.

How do we feel, knowing that one of our senators is in such close contact (for want of a better expression) with the US Embassy, and who might be influence by them and therefore influence our government?

I think it stinks.